The existing literature on experimentally induced pain indicates that
there are sex differences, with females displaying greater sensitivity
. In epidemiological studies, sex differences are also noted in the pr
evalence of a number of pain syndromes, with females reporting more se
vere pain, more frequent pain, and pain of longer duration. Complicati
ng the interpretation of pain differences between men and women in cli
nical samples are reports of sex differences in response to pain-reduc
ing medications. Studies in human subjects suggest that women respond
better to certain opioid analgesics than men following third molar ext
raction, but few studies have assessed sex effects in effectiveness of
topical anesthetics. The purpose of this study was to test for sex di
fferences in response to a topical anesthetic, Lidocaine, using double
blind, placebo controlled experimental methodology, in combination wi
th a magnitude matching psychophysical protocol using a pressure algom
eter. The subjects were 21 female and 23 male adult volunteers. Twenty
-four subjects (12 males and 12 females) were randomly assigned to the
Lidocaine condition and 20 subjects were randomly assigned to the pla
cebo control condition (9 males and 11 females). The effect size acros
s sex for subjects in the Lidocaine treatment condition on the respons
e bias variable was large indicating the males rated the stimuli as le
ss painful than the females. Sex differences were not observed for dis
criminability in the Lidocaine treatment condition. This study did not
show sex differences in the placebo condition. These results are part
icularly interesting in light of previous work that has shown similar
pain stimuli (pressure pain) to be the stimulation most sensitive to s
ex differences. Results of this study suggest that the protocol employ
ed (pressure pain stimulus with magnitude matching task) is sensitive
to both anesthetic treatment and sex differences and represents an imp
rovement in pain assessment methodology for use in experimental studie
s and in the clinic. (C) 1998 International Association for the Study
of Pain. Published by Elsevier Science B.V.